The invention relates to 3-wire switches for connecting a load to a power supply. There are four types of configurations of 3-wire switches: (1) a P type DC switch where current flows from a DC source through the switch first and then to the load; (2) an N type DC switch where current flows from a DC source first through the load and then through the switch, such that the load is hot even when the switch is off: (3) a P type AC switch where the hot AC line is wired first through the switch and then through the load; and (4) an N type AC switch where the hot AC line is wired first through the load and then through the switch, such that the load is hot even when the switch is off.
An installer must stock three different switch modules to service these four configurations. One type of switch module services the P type DC configuration. A second different switch module services the N type DC configuration. A third switch module services both the P type AC and N type AC configurations.